Compensation technique for color shift in displays

Abstract

A system for maintaining a substantially constant display white point over an extended period of operation of a color display formed by an array of multiple pixels in which each of the pixels includes multiple subpixels having different colors, and each of the subpixels includes a light emissive device. The display is generated by energizing the subpixels of successively selected pixels, and the color of each selected pixel is controlled by the relatives levels of energization of the subpixels in the selected pixel. The degradation behavior of the subpixels in each pixel is determined, and the relative levels of energization of the subpixels in each pixel are adjusted to adjust the brightness shares of the subpixels to compensate for the degradation behavior of the subpixels. The brightness shares are preferably adjusted to maintain a substantially constant display white point.

What is claimed is: 
     
       1. A method of maintaining a substantially constant display white point of a color display comprising an array of multiple pixels, each of the multiple pixels including multiple subpixels having different colors, and each of the multiple subpixels including a light-emissive device, the method comprising:
 receiving a video signal; 
 controlling the color of each selected pixel in the array of the color display by:
 determining initial brightness shares for the subpixels in the selected pixel on a basis of the video signal; 
 determining a color-shift behavior due to aging for a selected subpixel in the selected pixel; 
 determining increased brightness shares of at least one of the subpixels in the selected pixel other than the selected subpixel in the selected pixel, by increasing the initial brightness shares based on the determined color-shift behavior of the selected pixel, to compensate for the color-shift behavior of the selected subpixel, in order to maintain a substantially constant display white point of the color display; and 
 
 driving the at least one of the subpixels in the selected pixel using said increased brightness shares. 
 
     
     
       2. The method of  claim 1 , wherein the color-shift behavior of the selected subpixel is a shift in chromaticity coordinates of the selected subpixel. 
     
     
       3. The method of  claim 1 , wherein the increased brightness shares of the at least one of the subpixels in the selected pixel other than the selected subpixel in the selected pixel are increased by applying increases derived from a correction factor based on the determined color-shift behavior of the selected subpixel. 
     
     
       4. The method of  claim 1 , wherein the light-emissive device in each subpixel is an organic light-emitting diode (OLED). 
     
     
       5. The method of  claim 1 , wherein the color display is a red-green-blue (RGB) display or a red-green-blue-white (RGBW) display. 
     
     
       6. The method of  claim 1 , wherein the color-shift behavior of the selected subpixel is determined by:
 measuring data for the light-emissive device in the selected subpixel; and 
 relating the measured data to a corresponding color-shift behavior of the selected subpixel. 
 
     
     
       7. The method of  claim 6 , wherein the measured data is a voltage, a current, or a luminance of the light-emissive device in the selected subpixel. 
     
     
       8. The method of  claim 6 , wherein the measured data is related to the corresponding color-shift behavior of the selected subpixel by using a lookup table. 
     
     
       9. The method of  claim 6 , wherein the measured data is related to the corresponding color-shift behavior of the selected subpixel in accordance with an empirically determined dependency. 
     
     
       10. The method of  claim 1 , wherein the color-shift behavior of the selected subpixel is determined by monitoring the color-shift behavior of the selected subpixel as the selected subpixel ages. 
     
     
       11. A system for maintaining a substantially constant display white point, the system comprising:
 a color display comprising an array of multiple pixels, each of the multiple pixels including multiple subpixels having different colors, and each of the multiple subpixels including a light-emissive device; and 
 a controller for receiving a video signal and for controlling the color of each selected pixel in the array of the color display by:
 determining initial brightness shares for the subpixels in the selected pixel on a basis of the video signal; 
 determining a color-shift behavior due to aging for a selected subpixel in the selected pixel; 
 determining increased brightness shares of at least one of the subpixels in the selected pixel other than the selected subpixel in the selected pixel, by increasing the initial brightness shares based on the determined color-shift behavior of the selected pixel, to compensate for the color-shift behavior of the selected subpixel, in order to maintain a substantially constant display white point of the color display; and 
 driving the at least one of the subpixels in the selected pixel using said increased brightness shares. 
 
 
     
     
       12. The system of  claim 11 , wherein the color-shift behavior of the selected subpixel is a shift in chromaticity coordinates of the selected subpixel. 
     
     
       13. The system of  claim 11 , wherein the increased brightness shares of the at least one of the subpixels in the selected pixel other than the selected subpixel in the selected pixel are increased by applying increases derived from a correction factor based on the determined color-shift behavior of the selected subpixel. 
     
     
       14. The system of  claim 11 , wherein the light-emissive device in each subpixel is an OLED. 
     
     
       15. The system of  claim 11 , wherein the color display is an RGB display or an RGBW display. 
     
     
       16. The system of  claim 11 , wherein the color-shift behavior of the selected subpixel is determined by:
 measuring data for the light-emissive device in the selected subpixel; and 
 relating the measured data to a corresponding color-shift behavior of the selected subpixel. 
 
     
     
       17. The system of  claim 16 , wherein the measured data is a voltage, a current, or a luminance of the light-emissive device in the selected subpixel. 
     
     
       18. The system of  claim 16 , wherein the measured data is related to the corresponding color-shift behavior of the selected subpixel by using a lookup table. 
     
     
       19. The system of  claim 16 , wherein the measured data is related to the corresponding color-shift behavior of the selected subpixel in accordance with an empirically determined dependency. 
     
     
       20. The system, of  claim 11 , wherein the color-shift behavior of the selected subpixel is determined by monitoring the color-shift behavior of the selected subpixel as the selected subpixel ages.